U.S. Pat. No. 3,542,610 discloses a pyrotechnical smoke charge which consists of an inorganic oxidizing agent, a fuel and a smoke-producing oil. The components of the combustion charge are selected in such a way that the combustion temperature suffices to evaporate the oil, but not to burn it. This process produces sulfides and mercaptans which constitute environmental hazards and which are toxic to living organisms.
A further smoke charge is known from Swiss Patent No. A5 - 638 168. This charge consists of zinc oxide, ammonium perchlorate, of polychloroisoprene as a chlorine donator, a softening agent and ammonium chloride for buffering. This smoke charge produces a chemically neutral smoke in the pH-range of 5-7, but releases harmful heavy metals and chlorides.
It is thus an object of the invention to provide a smoke charge the pyrotechnical combustion charge of which produces a dense, well-camouflaging smoke that releases no toxic substances and is in principle environment-compatible.
This object is achieved by use of a hygroscopic oxidizing agent, a reducing agent consisting of porous carbon granules, and a polar solvent to bind the oxidizing agent to the carbon granules.
The resulting combustion charge produces the smoldering combustion desired in smoke charges. A substantial advantage of the invention is that non-combusted or partially combusted smoke charge portions dissolve in atmospheric humidity or in rain, with little distinction from common chemical fertilizers. deleterious environmental effects have been determined. No
The method according to the invention for preparing the smoke charge consists in a first method step of wetting active carbon with water in a mechanical mixer. In a second step ammonium nitrate is ground in a ball mill. In a further step the wetted active carbon is admixed to the ammonium nitrate in the ball mill, where the substances are mixed with one another to form the combustion charge.
Water has been found to give outstanding service as the polar solvent. Suitable oxidizing agents have been found to be nitrate salts and, in particular, ammonium nitrate. A range of particle sizes can be utilized in the invention. It is expedient to press-form the combustion charge mixture on a conventional press.
The present invention is suitable for the preparation of smoke charges for special marking purposes or charges for smoke-absorbing infrared radiation when color pigments and/or binders and/or metal particles are included in the charge mixture. The charge of the present invention may be used for smoke-producing ammunition as used on vehicles such as tanks, etc.